I needed to find a network backup solution that would backup our 6 Windows 2000 servers without much of a budget. After looking at a host of Open Source options I finally found one that just worked, BackupPC. It is elegant in the way that it can save space on the hard drive by using Linux's hard linking. Basically, it only saves one file once and creates hard links whenever another computer uses the same matching MD5 sum. I experienced close to the same savings as listed on thier website.
One example of disk use: 95 latops with each full backup averaging 3.6GB each, and each incremental averaging about 0.3GB. Storing three weekly full backups and six incremental backups per laptop is around 1200GB of raw data, but because of pooling and compression only 150GB is needed.
I installed BackupPC on a test system and it worked like a champ. I was able to very easily see what files were locked from Windows. I am currently having some issues because one of my production database servers has a file over 4 GB which seems to be a Samba limitation.
Another good option was Bacula. Bacula was my first choice because it had a Windows native client and also had plenty of enterprise options for future expandability. I believe that it is more efficient to spend time early on learning about the more complex system and adapting it to a simple task than discovering that you need to impliment a new technology because the current techonology doesn't scale very well.